Removing cadmium coating from AN bolts

I need to weld two cadmium coated AN (aircraft) bolt heads to a steel plate. What is the best way to remove the cadmium coating? Other than just sanding or putting then through a wire wheel?

Thanks

Rick H.

Reply to
Rick
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Reply to
Michelle P

If you are only doing two it is not worth your time going to any extreme measure. The stuff flashes off quickly and you are unlikely to contaminate the weld. make sure you are in a well ventilated area. Cadmium is more toxic than zinc coatings. Randy

Reply to
Randy Zimmerman

VERY toxic.

Zinc will give you flue-like symptoms that evening, and will generally dissipate.

Cad will give you the same symptoms, but you'll die before you realize that you're screwed.

--- Rich

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Reply to
Rich Lockyer

Which begs the question: What kind of respirator can be used to keep you from harmful welding fumes, grinding dust, etc. and be worn under your hood?

rvb

Reply to
Rick Barter

An air-line respirator is the safest bet. In it's simplest form, it's a scuba regulator attached by a long hose to a compressor suitable for delivering breathing gasses. It needs to be able to maintain about 140psi. They are commonly known as "Hooka" rigs and are often used by boat cleaning crews and pool guys.

The problem with such a DIY rig is that the scuba regulator does not cover your nose, and the standard hoses are susceptible to UV deterioration. A full face mask would be a problem under the hood (and would not be a suitable replacement for a true safety goggle)... not to mention very uncomfortable.

Replacing the compressor with a tank will give you between 80 and 160 minutes of air, depending on your breathing rate. Since we're not talking about something you'll be taking down 400 feet, you could easily make do with a $150 cheapie. The tank would be about $100 or so. A 40ft hose will run over $50 (I honestly haven't priced them, I think I paid $25 for my 7 footer that I use for diving). Filling the tank will be a problem... a paintball shop may do it for you, but I'd ask to see their air purity certs. If they give you any shit and accuse you of breathing the air, just tell them that you don't want to contaminate your tank. You want a "Grade-E" or better air analysis. Most common contaminates are hydrocarbons and water.

Personally, I don't touch Cad, and only work with very small welds on galvanized/zinc coated... like sticking nuts and carriage bolts to steel. A big fan, keep my face at arm's length out of the plume, and I still hold my breath during the weld and still don't inhale near the joint until it cools. Note, this is for hobby-level work. I wouldn't do that for a serious job.

--- Rich

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Reply to
Rich Lockyer

Reply to
Robert Ball

There are several alternatives. Short of a thousand dollar fully enclosed welding helmet with an elastic neck band and air supply there are several alternatives. I have tack welded hundreds of cad plated bolts and nuts in my career and am still here.... I think. A face mask with pancake filters will fit under your mask or the best is the rigs that have two flexible hoses that go over your shoulders with filter canisters hanging on your back. They run up around 200 dollars depending on quality. Randy

Reply to
Randy Zimmerman

Is this common practice in the USA to use SCBA gear ? I've never seen it in the UK.

Over here our "supplied air" helmets use a much simpler system without the demand valve. There's an air compressor, either an oil-free screw compressor supplying clean air, or a standard workshop compressor running into an expensive charcoal filter. This then supplies a hose and there's a simple adjustable flow rate valve on the helmet. There's no demand valve, but the compressor can supply plenty of air so there's simply an over-supply. This is a good thing, as it also maintains a positive pressure in the mask and so sealing is less important.

SCBA gear is only used by firemean and chemical spill people, so as to avoid the air umbilical. Sealing the masks is a problem, so no beards and they needs to be carefuly adjusted to head size. You also need some training (one day course) to use it.

Reply to
Andy Dingley

Reply to
Robert Ball

Not in the workplace. I was referring to a basic DIY setup that could be made from items possibly already in posession or easily available.

--- Rich

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Reply to
Rich Lockyer

Excellent suggestion. If buying 2nd hand, make sure that the exhaust valve mushroom functions properly. Breathing through a couple of

2-foot hoses without a functioning exhaust valve will rapidly overload you with CO2.

--- Rich

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Reply to
Rich Lockyer

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